 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=s, initial-scale=1.0">
    <title>Documen</title>
</head>
<body>
    <script>
        var yu = prompt('请输入小明的语文成绩')
        var sh = prompt('请输入小明的数学成绩')
        var wa = prompt('请输入小明的外语成绩')
        var letm = yu*1 + sh*1 + wa*1;
        alert('总成绩：'+letm);
    </script>
</body>
</html>